Larry's Blog

Response to Gran Turnio

larrykeegan — Thu, 18 Jun 2009 07:07:57 +0000

CLOCK ESCAPEMENT

larrykeegan — Tue, 27 Feb 2007 22:08:03 +0000

Here is a look at my Verge & Foliot escapement
in action
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ADVICE ON CMOS IC’s

larrykeegan — Wed, 09 Aug 2006 21:17:50 +0000

THIS IS A LETTER I SENT
to George Gallant, Jim Morris
and Jim Fiske
hi
just realized something troubling
I was reading some hints for using the PIC
microcontrollers and found this:
“unconnected port bits should never
be set up as inputs”
“when floating, CMOS inputs can flip rapidly
between states and cause excessive current draw,
heating and even damaging the PIC”
So – set all unused bits of ports to outputs.
I went back to one of my books talking about
CMOS IC’s and noticed this warning:
ALL unused inputs MUST be connected to Vdd(+) or Vss(gnd)
otherwise erratic chip behavior and
excessive current consumption will occur.
other rules for CMOS were NEVER connect
an input signal to a cmos circuit when
the power is off.
another curious warning was to
avoid slowly rising and falling input signals
since they cause excessive power
consumption. it recommended
rise times faster than 15 usecs
I think I have been lucky so far
but I’m certainly going to observe
these precautions.
Regards.
Larry Keegan in Stoneham, MA

ALPHANUMERIC DISPLAY AND KEYBOARD

larrykeegan — Fri, 26 May 2006 19:11:01 +0000

Do you realize you can pick up older keyboards for one dollar! I have a few and use them to interface with my computer chips. I have done more work on my alphanumeric LCD (liquid crystal display). I can now set addresses and send ascii characters to these locations. The lcd controller automatically increments or decrements, each time you write to an address.

I am now able to read the contents of the DD RAM. The bytes of this memory correspond to the characters appearing on the display. The character generator is transparent to the programmer and produces the pixels that form the characters displayed. A very interesting development is serial rather than parallel LCDs. These seem to cost
$45 and up whereas the parallel type go for 10 to 20. It is desirable to have LED backlighting for good visibility.

SONG MAKING CIRCUIT

larrykeegan — Fri, 26 May 2006 17:22:35 +0000

Here is a version of a circuit that plays music. The program actually calls subroutines called doe,ray,me,far,sew,la,tea,doo. I have done lots of pgms on generating sounds, but this one attempts to get accurate mnotes of the musical scale. Some of the ideas came from an artice by G. Y. Xu in Nuts & Volts magazine.
So far this circuit plays Westminster Chimes and the theme played a race tracks for the start of the race. My circuit plays the notes as regular tones or as bell chimes.

PARALLEL & SERIAL MEMORY CHIPS

larrykeegan — Sat, 29 Apr 2006 16:55:44 +0000

Here is the very interesting story about 2 kinds of memory chips. One is a parallel type and one is a serial type. The serial memory on the right has only 8 pins. The traditional memory chip has 15 pins for address, and 8 pins for data. Obviously to access this chip, a lot of wiring is needed! Then how can the 8 pin chip be accessed? The answer is by sending a serial stream of data to it. This serial stream might be as follows:
command to write, part of address, other part of address, data to be written
This would be 4 bytes of info sent to the memory chip, along with a clock pulse on another line to guide the reception of the info.
So, can you see the tradeoffs?! The chip with all the pins is heavy on HARDWARE and wiring. The chip with the few pins is heavy on SOFTWARE and intricate programming.
Well, I opted for the small serial chip which can hold 4096 bytes of info. I had to grapple with the intricacies of software. I discovered that I had a bad solder connection on the CLOCK line SCK going from the PIC to the mem chip. I finally have it under control and have dozens of plans for usinbg it. By the way, this is an EEPROM chip. It is a non-volatile memory, but you can write over it up to one million times. These chips only cost about a buck.

KEYBOARD INTERFACE FOR MICROCONTROLLER

larrykeegan — Sun, 26 Feb 2006 20:23:50 +0000

Here is a look at how I am hooking up a PC KEYBOARD to my microcontroller – the PIC16F628.

I found an article on the inernet that explained the protocol of a PC keyboard. Not as bad as I thought! Only 2 lines for CLOCK and DATA. Other 2 lines for +5 volts and a return. The keyboard sends serially, but not the asciii codes themselvesw, but scan codes, which have to be translated. I had to do a lot of debugging of my code but I’m having success now.
I can also display alphanumeric data on my LCD, make it blink, and have it rotate across the screen. Much fun!!

ALPHANUMERIC LCD DISPLAY

larrykeegan — Thu, 09 Feb 2006 14:53:53 +0000

SUCCESS with programming my alphanumeric LCD display!!!

WATER ON STONE

larrykeegan — Fri, 27 Jan 2006 21:31:00 +0000

can’t feel the rain on their face any more

can’t go to war

I pass the stones

one by one in the storm

and when the rain has stoppped

there’s no need to warm

in the sun

what’s done is done

but the rows are alive

with memories. This one

traveled here, this one there

one breathed his last

in Normandy air

whether it’s spring, or roses

doesn’t mean a thing

none of them is alone

only me, watching water

on the face of a stone

Larry Keegan

can’t feel the rain on their face any morecan’t go to warI pass the stonesone by one in the storm
and when the rain has stopppedthere’s no need to warmin the sunwhat’s done is done
but the rows are alivewith memories. This onetraveled here, this one thereone breathed his lastin Normandy air
whether it’s spring, or rosesdoesn’t mean a thingnone of them is aloneonly me, watching wateron the face of a stone
Larry Keegan

STEEPLES

larrykeegan — Fri, 27 Jan 2006 21:25:00 +0000

it’s Saturday night

and all is well

nobody’s going to heaven

and nobody’s going to hell

there’s road rage on the highway

600 waiting on death row

for some the spring is coming

for others – I don’t know

there’s a war that’s killed ten thousand

it started because no one said no

some hope it will turn out well

there were lies, and a command to go

it’s Saturday – people head to church

on Sunday they will say their prayers

steeples make good cell phone antennas

millions bow their heads

but there may be no one upstairs

Larry Keegan

it’s Saturday night and all is wellnobody’s going to heavenand nobody’s going to hell
there’s road rage on the highway600 waiting on death rowfor some the spring is comingfor others – I don’t know
there’s a war that’s killed ten thousandit started because no one said nosome hope it will turn out wellthere were lies, and a command to go
it’s Saturday – people head to churchon Sunday they will say their prayerssteeples make good cell phone antennasmillions bow their headsbut there may be no one upstairs
Larry Keegan